Aftertreatment system for simultaneous emissions control in stationary rich burn engines

Abstract

A catalyst system may include a three-way catalyst that may receive exhaust gases from an engine and convert the exhaust gases to first converted exhaust gases. An ammonia slip catalyst may receive the first converted exhaust gases and convert the first converted exhaust gases to second converted exhaust gases. A hydrocarbon oxidation catalyst may receive the second converted exhaust gases and convert the second converted exhaust gases to third converted exhaust gases.

What is claimed is: 
     
       1. A system comprising:
 a three-way catalyst that receives exhaust gases from an engine and converts the exhaust gases to first converted exhaust gases; 
 an ammonia slip catalyst that receives the first converted exhaust gases and converts the first converted exhaust gases to second converted exhaust gases; 
 a hydrocarbon oxidation catalyst that receives the second converted exhaust gases and converts the second converted exhaust gases to third converted exhaust gases wherein the hydrocarbon oxidation catalyst comprises a precious metal loading comprising palladium and platinum, and a ratio of the palladium to the platinum is greater than one; and 
 a mid-bed air injection system that injects air into the first converted exhaust gases upstream of the ammonia slip catalyst and injects air into the second converted exhaust gases upstream of the hydrocarbon oxidation catalyst. 
 
     
     
       2. The system of  claim 1 , wherein the ammonia slip catalyst comprises a precious metal loading and a zeolite coating. 
     
     
       3. The system of  claim 2 , wherein the precious metal loading comprises at least one of platinum or palladium. 
     
     
       4. The system of  claim 1 , wherein the ammonia slip catalyst converts carbon monoxide in the first converted exhaust gases to carbon dioxide. 
     
     
       5. The system of  claim 4 , wherein the ammonia slip catalyst converts ammonia in the first converted exhaust gases to nitrogen. 
     
     
       6. A method comprising:
 receiving exhaust gases from an engine at a three-way catalyst; 
 converting, at the three-way catalyst, the exhaust gases to first converted exhaust gases; 
 injecting air, via a mid-bed air injection system, into the first converted exhaust gases upstream of an ammonia slip catalyst; 
 receiving the first converted exhaust gases at the ammonia slip catalyst; 
 converting, at the ammonia slip catalyst, the first converted exhaust gases to second converted exhaust gases; 
 injecting air, via the mid-bed air injection system, into the second converted exhaust gases upstream of the hydrocarbon oxidation catalyst; 
 receiving the second converted exhaust gases at the hydrocarbon oxidation catalyst; and 
 converting, at the hydrocarbon oxidation catalyst, the second converted exhaust gases to third converted exhaust gases, wherein the hydrocarbon oxidation catalyst comprises a precious metal loading comprising palladium and platinum, and a ratio of the palladium to the platinum is greater than one. 
 
     
     
       7. The method of  claim 6 , wherein converting, at the ammonia slip catalyst, the first converted exhaust gases to the second converted exhaust gases comprises converting carbon monoxide in the first converted exhaust gases to carbon dioxide. 
     
     
       8. The method of  claim 6 , wherein converting, at the ammonia slip catalyst, the first converted exhaust gases to the second converted exhaust gases comprises converting ammonia in the first converted exhaust gases to nitrogen. 
     
     
       9. The method of  claim 6 , wherein the ammonia slip catalyst comprises a precious metal loading and a zeolite coating. 
     
     
       10. The method of  claim 9 , wherein the precious metal loading comprises at least one of platinum or palladium. 
     
     
       11. A system comprising:
 an internal combustion engine that generates exhaust gases; 
 a three-way catalyst that receives the exhaust gases and converts the exhaust gases to first converted exhaust gases; 
 an ammonia slip catalyst that receives the first converted exhaust gases and converts the first converted exhaust gases to second converted exhaust gases; a hydrocarbon oxidation catalyst that receives the second converted exhaust gases and converts the second converted exhaust gases to third converted exhaust gases, wherein the hydrocarbon oxidation catalyst comprises a precious metal loading comprising palladium and platinum, and a ratio of the palladium to the platinum is greater than one; and 
 a mid-bed air injection system that injects air into the first converted exhaust gases upstream of the ammonia slip catalyst and injects air into the second converted exhaust gases upstream of the hydrocarbon oxidation catalyst. 
 
     
     
       12. The system of  claim 11 , wherein the ammonia slip catalyst comprises a precious metal loading and a zeolite coating. 
     
     
       13. The system of  claim 11 , wherein the ammonia slip catalyst converts ammonia in the first converted exhaust gases to nitrogen. 
     
     
       14. The system of  claim 11 , wherein the ammonia slip catalyst converts carbon monoxide in the first converted exhaust gases to carbon dioxide.